Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual raça tem duração de 12 horas?
 ###Tabelas: CREATE TABLE 2010_regular_season_football_standings (2010_regular_season_football_standings_id AUTO_INCREMENT PRIMARY KEY, School VARCHAR, Team VARCHAR, Division Record VARCHAR, Overall Record VARCHAR, Season Outcome VARCHAR) CREATE TABLE round_six (round_six_id AUTO_INCREMENT PRIMARY KEY, Pick # INT, CFL Team VARCHAR, Player VARCHAR, Position VARCHAR, School VARCHAR) CREATE TABLE schedule (schedule_id AUTO_INCREMENT PRIMARY KEY, Race VARCHAR, Length VARCHAR, Class VARCHAR, Circuit VARCHAR, Date VARCHAR) CREATE TABLE year-by-year_stats (year-by-year_stats_id AUTO_INCREMENT PRIMARY KEY, Team INT, Games Played INT, Wins INT, Losses INT, Winning Percentage INT, Points For INT, Points Against INT, Point Differential INT) CREATE TABLE texas_counties_ranked_by_per_capita_income (texas_counties_ranked_by_per_capita_income_id AUTO_INCREMENT PRIMARY KEY, County VARCHAR, Per capita income VARCHAR, Median household income VARCHAR, Median family income VARCHAR, Population INT, Number of households INT)  
SELECT Race FROM schedule WHERE Length = 12 hours